Calibrating device for radiation gauge



Feb. 22, 1966 w. P. NEAL, JR

CALIBRATING DEVICE FOR RADIATION GAUGE Filed July 9, 1963 nmN M M 5 m Y N R w m M rm m 0 Y B W United States Patent 3,236,090 CALIBRATING DEVICE FOR RADIATION GAUGE William P. Neal, Jr., Richmond, Va., assignor to The American Tobacco Company, New York, N.Y., a corporation of New Jersey Filed July 9, 1963, Ser. No. 293,792 Claims. (Cl. 73-1) This invention relates to a calibrating device for a gauge in which radiation passing through an object from a source of radiation is measured to determine the density of the object.

A gauge of this type is frequently used in cigarette making machines to control the density of tobacco in a cigarette rod. In producing the rod, tobacco is delivered at a controlled rate onto a strip of paper formed into a generally U-shaped trough, then the ends of the trough are overlapped and sealed to form a rod which is ultimately cut into cigarette lengths. In order to control the density of the cigarettes, and hence their tobacco content, the cigarettes are passed through a guide which directs their longitudinal path through a radiation gauge. The radiation, generally beta rays from a suitable source, passes through each cigarette as the cigarette moves axially through the gauge, and the radiation which is not adsorbed by the cigarette is measured by a detector. The strength of the detected radiation is thus a measure of the density of the tobacco in the cigarette, and the resulting signal is used to control the rate of feed of tobacco to the rod-forming stage.

Whenever a cigarette making machine provided with a radiation-type control gauge is shut down with a resulting upset in the control of feed tobacco for the rod-forming stage, a considerable period of the subsequent starting-up operation must be devoted to adjusting the tobacco feed for the desired tobacco density in the cigarettes. There is need, therefore, for a device for calibrating the radiation gauge of each cigarette making machine so that the gauge and the machine can be promptly re-set to assure proper tobacco density control as soon as that machine is re-started.

I have now devised a calibrating device for radiationoperated gauges that measures the amount of radiation adsorbed by the measured object. My novel calibrating device comprises a hollow tube of radiation-permeable material, the interior bore of the tube being tapered to provide tube walls of axially varying density and the exterior of the tube being provided with at least one longitudinally extending flattened surface. Axial centering means are provided for positioning the axis of the tube in a predetermined position in the gauge with the tube axis normal to the flow of radiation in the gauge, and longitudinal positioning means are provided for moving the tube along said predetermined axial position so as to obtain the desired degree of adsorption of radiation. Rot'ating means are further provided for rotating the tube about its axis at a predetermined speed so as to establish a standard for the gauge reading which is characteristic for the desired density measurement.

These and other novel features of the calibrating device of the invention will be more readily understood from the following description taken in conjunction with the drawings in which:

FIG. 1 is a side elevation, partly broken away and partly in section, of the calibrating device mounted in the cigarette guide holder of a maker;

FIG. 2 is a section taken along line 2-2 in FIG. 1;

FIG. 3 is a section taken along line 3-3 in FIG. 1;

FIG. 4 is a section taken along line 44 in FIG. 1; and

FIG. 5 is a section taken along line 5-5 in FIG. 1.

The calibrating device of the invention is shown in FIG. I mounted in one of the cigarette guide holders 10 conventionally secured to a mounting plate 11 of the detector assembly. These guide holders normally hold guides which direct the path of cigarettes along an axial path between a source of radiation and a detector for the radiation that passes through the moving cigarettes. Between the cigarette guide holders 10 there is mounted on the plate 11 a conventional beta ray source-detector 12 adapted to detect beta rays from a source on the viewing side of [the center line of the two holders 10.

The calibrating device consists of two sections which are adjustably interconnected. One section is the mounting element and the other section is a tube-holding, positioning and rotating element. The mounting element section comprises a cylindrical mandrel portion 13 integrally formed with a cylindrical body portion 14 of larger diameter than the mandrel portion. The mandrel portion is eccentrically positioned with respect to the axis of the body portion, and both portions are provided with a central bore 15 which is axially positioned in the body portion and hence eccentrically positioned within the mandrel portion. Inasmuch as the cigarette guide holder 10 is conventionally provided with an eccentric bore which the mandrel portion 13 is designed to fit, rotation of the mandrel portion within the guide holder permits axial alignment of the bore of the mounting element section with the normal axis of cigarettes passing through the radiation gauge assembly. The mandrel is held in this aligned position by a set screw 16 mounted in the guide holder.

The other section of the calibrating device comprises a double sleeve body portion 17, the outer sleeve 17a being adapted to fit slidingly over the outside of the body portion 14 of the mounting element section and the inner sleeve 1712 being adapted to fit slidingly within the bore 15 of the mounting element section. The inner bore 18 of the inner sleeve 17b is provided at each end thereof with a bearing 19 in which is mounted a calibrating tube drive shaft 20. The drive shaft extends rearwardly out of the double sleeve body portion 17 and through a mounting plate 21 on which both the double sleeve body portion and a synchronous electric motor 22 are mounted. The motor is connected by gears 23a and 23b to the drive shaft 20. The inner end of the drive shaft is force-fitted into a calibrating element 24 of plastic material such as a methyl methacrylate resin. The end of the calibrating element mounted on the shaft is solid except for a recess into which the inner end of the drive shaft 20 is fitted. The major portion of the calibrating element is provided with a tapered bore 25 which thus forms a tubular portion 26 having a side wall of axially varying thickness or density. As shown in FIG. 2, at least one, and preferably two, diametrically opposite fiat areas 26a are provided lengthwise of the tubular portion 26 so as to provide a discontinuity in the thickness or density of any selected axial portion of the tube when it is rotated about its axis.

The two sections of the calibration device of the invention are interconnected by an adjusting element which, after the mandrel portion 13 of the mounting section is positioned in the guide holder 10, permits controlled laxial movement of the tapered tube 26 so as to present any desired thickness of tube in the path of the radiation through the gauge. This adjusting element comprises an arm 27 which is force-fitted onto the inner end of the mandrel portion 13. The end of the arm is provided with a slot 28 adapted to engage .a narrow neck portion 29 of an adjusting screw 30. The other end of the screw engages a threaded angle bracket 31 which is screwfastened to the double sleeve body portion 17. Thus, as the knurled knob of the screw 30 is turned, it moves the double sleevetody portionll'Z either..toward. .lor .away.

from the mounting element section. This motion, which is purely axial as insured by a key 32 in the double sleeve bodyportion moving. ina keyway. 33 -in the mandrel element bodyv portion 14, imparts the desired axial movement to' the calibrating tube 24.

: In'operation of the calibrating device of the invention, the object is to establish a meter reading which is characteris'tic of .a'degree 'of adsorption of radiation in' any individual gauge that corresponds to the desired operataxis of the mandrel, is thus axially centered in the gauge. The gear train is turned by hand until the flattened surfaces produces .a variation in radiation-adsorption which produces as corresponding fluctuations in the detector meter.

reading for future reference, the subsequent -adjustment of the gauge to produce the desired machine operationcan be readily achieved by adjusting the knurled screw so as to obtain :a null reading which will produce the recordedmeter reading forthat gauge-machine combination when the tube is rotated at the aforesaid constant speed.

In lieu of using a meter for establishing the desired position of the calibrating, tube .in the gauge,.one can refer to a cal-ibratingscale 34 on the cylindrical body portion 14 of the mounting element section.- .The position of this body portion can be read from that port-ion of the scale exposed beyond the inboard edge of vthe outer sleeve 17a of the double sleeve body portion. A further ,vernier reading is obtained from a circumferential scale 35 on the knurled knob of the adjusting screw 30, this scale being read against a scribe mark 36 on the adjusting element arm 27. v

, It will be appreciated, accordingly, that the calibrating device of the invention can be readily set, either by reference to the gauge meter or to the scales on-the device, or to both, as a means of double checking, so as to obtain a recordable condition which can be reproduced whenever desirable for setting up the optimum operating condition of a cigarette maker provided with a density radiation gauge. 7

1.. A device for calibrating a gauge in which radiation passing through an object from a source of radiation is measured to determine the density of the object, the device comprising a hollow tube of radiation-permeable material, the interiorbore of the tube being tapered to .provide tube walls of axially varying density and the exterior of the tube being provided with .at least one longitudinally extending flattened surface, axial centering means for positioning the axis of the tube in a predetermined position in the gauge with the tube axis normal to the flow of radiation in the gauge, longitudinal positioning means for moving the tube along said predetermined axial position, and rotating means for rotating the tube about its axis at a predetermined speed.

machine A.,device forcalibrating. a gauge in which radiation passing through an object from a source of radiation is measured to determine the density of the object, the device comprising a hollow tube of radiation-permeable material, the interior bore of the tube being taper-ed to provide "tube walls of axially varying density and the exterior, of the tube being provided with two longitudinally ext-ending flattened surfaces positioned diametrically opposite one another, axial centering means for positionsentative of the desired density of a cigarette. The motor f of the calibrating device is then started, and the resulting rotati-on of the tube- With its-one or more flattened sur- By rotating the tube at a constant predetermined speed, the reading of the magnitude of the fluctuation of l the rneter is-a reproducible value which ischaracteristic for the gauge being calibrated. By recording this meter ing the axis-of the tube in a predetermined position in the gauge wit-h the tube axis normal to the flow of radiation in the gauge, longitudinal positioning means for moving the tube along said predetermined axial position, and

i rotating means for rotating the tube about its axis at a predetermined speed.

V 3. Adevice for calibrating a gauge in which radiation passing through an object from a source of radiation is measured to determine the density of the object, the device comprising a :hollow tube of plastic material, the

interior bore of the tube being tapered to provide tube walls ofaxially varying density and the exterior of the tube being provided with at least one longitudinally extending flattened surface, axial centering means for positioning the axis of the tube in a predetermined position in the gauge with the tube axis normal to the flow of radiation in the gauge, longitudinal positioning means for moving the tube along said predetermined axial position, and rotating means for rotating the tube about its axis at a predetermined speed.

. 4. A devicefor calibrating a gauge in which radiation passing through a cigarette from a source of radiation is measured to determine the density of the cigarette, the device comprising a'h-ollow tube of radiation-permeable material, the interior bore of the tube being tapered to provide tube Walls of axially varying density and the cxterior of the tubebeing provided with at least one longitudinally extending flattened surface, rota-ting means for rotating the tube about its axis at a predetermined speed, axial centering means for positioning the axis of the tube in a position in the gauge corresponding to the position of .a cigarette to be measured by the gauge, and longitudin-a1 positioning means for moving the tube along said predetermined axial position.

5. A device for calibrating a gauge in which radiation from a source thereofis measured after passing through a cigarette moving through a guide held in fixed position with respect to the source of radiation in order to determine the density of the cigarette, the calibrating device comprising a hollow tube of radiation-permeable material, the interior bore ,of the tube being tapered to provide tube walls of axially varying density and the exterior of the tube being provided with at least one longitudinally extending flatten-ed surface, axial centering means comprising a hollow mandrel adapted to be held by the cigarette guide holder for positioning the axis of the tube in a position in the gauge corresponding to the position of a cigarette moving through the gauge, longitudinal tube positioning means extending through the hollow mandrel, tube supporting means rotatably mounted in the tube positioning means, rotating means for rotating the tube about its axis at a predetermined speed, and adjusting means for moving the tube positioning means longitudinally of the tube so as to move the tapered tube into a position within the gauge such that the density of the tube corresponds to the density of the cigarette. I

References Cited by the Examiner UNITED STATES PATENTS LOUIS R- PRINCE, Primary Examiner. 

1. A DEVICE FOR CALIBRATING A GAUGE IN WHICH RADIATIOIN PASSING THROUGH AN OBJECT FROM A SOURCE OF RADIATION IS MEASURED TO DETERMINE THE DENSITY OF THE OBJECT, THE DEVICE COMPRISING A HOLLOW TUBE OF RADIATION-PERMEABLE MATERIAL, THE INTERIOR BORE OF THE TUBE BEING TAPERED TO PROVIDE TUBE WALLS OF AXIALLY VARYING DENSITY AND THE EXTERIOR OF THE TUBE BEING PROVIDED WITH AT LEAST ONE LONGITUDINALLY EXTENDING FLATTENED SURFACE, AXIAL CENTERING MEANS FOR POSITIONING THE AXIS OF THE TUBE IN A PREDETERMINED POSITION IN THE GAUGE WITH THE TUBE AXIS NORMAL TO THE FLOW OF RADIATION IN THE GAUGE, LONGITUDINAL POSITIONING MEANS FOR MOVING THE TUBE ALONG SAID PREDETERMINED AXIAL POSITION, AND ROTATING MEANS FOR ROTATING THE TUBE ABOUT ITS AXIS AT A PREDETERMINED SPEED. 